#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    ifstream cin("deque.in") ;
ofstream cout("deque.out") ;
    int n,k,a[5000001],i,s,b[5000001],h=1,t=0;
    cin>>n ;
    cin>>k ;
    for (i=1;i<=n;i++) ;
    {
cin>>a[i];
    cin.close() ;
   if(b[h]==i-k) h++;
while(h<=t&&a[i]<=a[b[t]]) t--;
b[++t]=i;
if(i>=k) s+=a[b[h]];}
cout<<s;
cout.close() ;
}